I used to feed what the local elevator sold and I seemed to always have some kind of problem - - retained placentas, weak calves, unthrifty cows then started on a year around mineral program that includes IGR about 9 months of the year in this area and I now go and monitor my cattle instead of treating them - - - I have not pulled a calf in years, am calving in less than 45 days  ( I'm going for less than 30 days) having about 5% of the cows with twin calves!  I feel most of the improvment is in the minerals - - you need to sample your forage and hay because with different fertilizer treatments your requirements might now be what your neighbors are.  Good mineral programs DO NOT COST - - - THEY PAY!!!  I have not tried the cargil "right now" program but it seems to make sense to me.  Get rid of all salt blocks - - they were better than nothing when I started feeding cattle in the 1950s but then my WD45 Allis Chalmers was better at pulling a plow than my horse - - - the WD45 is gone and so are my salt blocks.